Is stove ash useful?

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We have just invested in a brilliant solid-fuel stove. However, from the logs and coal consumed it generates copious quantities of ash. It seems a shame not to dig this in or mix it with the compost. But can one use too much and is there a difference between wood and coal ash?

Martin Press, via email

There is considerable confusion about the usefulness of ash in gardens, so perhaps this is a good opportunity to throw some light on the issue. Ash from garden bonfires (consisting mostly of green, sappy roots and prunings) contains some potash and other nutrients in small quantities considered enough to be used, traditionally, as a top dressing around soft fruit before other fertilisers were generally available. Ash from woodier bonfires has a slight liming effect on the soil, which is regarded as useful by vegetable growers. However, such ash should not be spread about where potatoes are to be grown, since they need a lower soil pH.

To the nitty-gritty of your question: pure log ash from stoves contains some, but fewer, useful nutrients than bonfire ash. Small amounts added to a compost bin mixture won’t do any harm – or much good either. Ash derived from coal or a mixture of coal and wood (or, indeed, from fires where treated wood has been burnt and from barbecue briquettes) should be binned.